The present invention relates to a generator, a nacelle, and a mounting method of a nacelle of a wind energy converter.
A wind energy converter is a rotating machine which converts the kinetic energy in wind into electricity and feeds the electricity into the electrical grid.
A wind energy converter generally includes a nacelle disposed on a tower. The nacelle (also called gondola) includes a rotor head equipped with blades, and a main shaft connected to the rotor head, also called hub, which integrally rotates with the rotor head. Moreover, the nacelle can rotate around a vertical axis so as to actively or passively follow the wind direction.
A first type of nacelle further includes a gear box connected to the main shaft that rotates upon receiving the wind power supplied to the blades, and a generator driven by an output shaft from the gear box. According to the wind energy converter having this structure, the rotor head equipped with the blades converts wind power into a torque, and the main shaft rotates to generate a first rotational speed. The first rotational speed is increased via the gear box connected to the main shaft, and a corresponding second larger rotational speed is transmitted to the rotor of the generator.
A second type of nacelle without gear box uses direct drive turbines with AC generators with variable frequency. Special high power electronics convert from variable frequency to constant frequency in the grid.
In present wind energy converters, the mounting of the preassembled nacelle on the tower using a crane is quite difficult and complex since the single components should be treated with respect. The nacelle can either be completely pre-assembled or can be sequentially mounted on top of the tower divided into plural segments.
The mounting method using divided segments of the nacelle simplifies the transport using the crane; however, it requires further complicated mounting steps on top of the tower.
Since the nacelle components are heavy, typically weighing a total of between 50 and 100 tons, both transport and mounting are generally problematic.
EP 1 921 310 A1 discloses a nacelle of a wind power plant is known that includes a generator and a gear box arranged in series which operate together, wherein a first bearing supports the rotor at the input side of the gear box and a second bearing supports the rotor at the output side of the generator.
For nacelles without a gear box, the rotor is normally supported by a first bearing on the input side of the generator and a second bearing at the output side of the generator.
This is necessary because the air gap between the rotor and the stator of the generator normally ranges between 2 and 6 mm. In other words, the air gap is very small and the input and output bearings are necessary in order to avoid the detrimental influence of mechanical tolerances.